Arc-extinguishing chambers for alternating current utilizing permanent magnets



Feb. 13, 1968 E. MAGGI 3,369,095

ARC-EXTINGUISHING CHAMBERS FOR AL'I'ERNATING CURRENT UTILIZING PERMANENT MAGNETS '7 Sheets-Sheet 1 Filed May 12, 1964 INVENTOR. ERNESTO HHGGI M W W E. MAGGI 5 ARC-EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT Feb. 13, 1968 7 Sheets-Sheet 2 UTILIZING PERMANENT MAGNETS Filed May 12, 1964 25 a4 31' LB 35' INVENTOR.

ERNESTU mam WWW Feb. 13, 1968 E. MAGGI 3,369,095

ARC'EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT UTILIZING PERMANENT MAGNETS Filed May 12, 1964 7 Sheets-Sheet I5 INVENTOR ERNESTO MHGGI BY W 0 W Feb. 13, 1968 E. MAGGI 3,359,095

ARC-EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT UTILIZING PERMANENT MAGNETS Filed May 12, 1964 '7 SheetsSh et 4 ,4- 59 22 m 45 a a i I l I 41 i I i i i l i 64 a s i I I I Q I 1 46 .4 I 1 i I 59 62 59 LD 59 62 INVENTOR. ERNE STO MAGS! BY WWW W,

Feb. 13, 1968 E. MAGGI ARC-EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT UTILIZING PERMANENT MAGNETS Filed May 12, 1964 7 Sheets-Sheet 5 INVENTOR. ERNESTO HHGG/ m 0/14/0 MW,

E. MAGGI 3,369,095 ARC-EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT Feb. 13, 1968 UTILIZING PERMANENT MAGNETS Filed May 12; 1964 '7 Sheets- Sheet 8 INVENTOR.

E. MAGGI 3,369,095 EXTINGUISHING CHAMBERS FOR ALTERNATING CURRENT 7 S T E N G A M T N E N A M R E P G N I Z I L I T U INYVENTOR. ERNEST!) MAGG/ Feb. 13, 1968 ARC Filed May 12, 1964 United States Patent ARC-EXTINGUISHING CHAMBERS FOR ALTER- NATING CURRENT UTILIZING PERMANENT MAGNETS Ernesto Maggi, Viale Vittorio Veneto 69, Bergamo, Italy Filed May 12, 1964, Ser. No. 366,703 Claims priority, application Italy, Jan. 29, 1964, 1,756/64: Apr. 9. 1964, 7,720/64 5 Claims. (Cl. 200-147) ABSTRACT OF THE DISCLOSURE The disclosure comprises an arc-extinguishing chamber for AC. arcs comprising at least two sections each including at least one couple of permanent magnets, the couples of the two sections defining, between facing surfaces thereof, a path of travel for the moving contact, separating from a stationary contact, and generating an arc, the couples of each section extending to only one respective side of the path of travel. Each couple includes ermanent magnet means providing at least a pair of opposite polarity poles in facing spaced relation to define therebetween an air gap in a permanent magnet circuit, and each section defines, between the poles of its couples, a narrow and tortuous path, for the are, which is of increasing length so as to displace the are rapidly away from the path of travel of the movable contact.

Background of the invention My invention relates, generally, to arc-extinguishing chambers for electric circuit interrupters and, more especially, to such extinguishing chambers which employ permanent magnets in order to produce magnetic fields capable of displacing the alternating current electric are for the purpose of elongating it, cooling it and expediting its extinction.

The various means provided up to the present time in order to accomplish the extinction of the alternating current electric are which is drawn upon the separation of the movable contact from the stationary one of circuit breakers, contactors, starters, switches and similar apparatus performing opening operations of electric circuits are well known to those who are skilled in the art.

The appropriate use of some of such means has permitted to accomplish the extinction of the alternating current electric are within times of very short durations which, for some electric current intensities, have approached one half cycle of the frequency of the current flowing in the arc.

There are thus extinguishing chambers into which the electric arc is driven to enter, under the action of magnetic fields produced by electromagnets energized by the same current flowing in the circuit to be interrupted, and which are so shaped and disposed as to force the arc to assume successive positions adapted to elongate and confine it rapidly between insulating walls capable of cooling and deionizing it so as to cause its extinction at the instant the current goes through its natural zero value. Such action of the field produced by the electromagnets, and which may be called the main field, together with the effect of the currents own magnetic field, is proportional to the current intensity and will he therefore relatively weak for currents having small intensities. For this reason it has been often necessary to add to such chambers some auxiliary means, such as air jets or insulating gas jets produced by puffers operated either mechanically by the leverage mechanism actuating the circuit breakers moving contacts, or electrically, by electromagnets properly energized, at the time of contacts separation.

It is also known that inside of the extinguishing chambers, conventionally identified as labyrinth type chambers, the electric arc is forced to follow paths having the shape of zig-zag lines, of snake-like lines, or of solenoidal loop which, although causing substantial increases of the arc length, produce also important reductions of length for the the sections of the arc path disposed transversely to the flux lines of the main magnetic field produced by the electromagnets energized by the same current flowing in the circuit to be interrupted and which has caused the electric arc to enter initially inside the labyrinth of the chambers. When the electric arc has taken inside of .such a chamber one of the above path shapes, a substantial part of its length remains thus subjected only to the action of the magnetic field produced by the current itself and will therefore present different performances, in relation to the various current values, with respect to are duration and number of arc reignitions before its final extinction.

Besides, such types of chambers are not capable of causing rapid and significant displacements of the electric are where the medium in which they are immersed is constituted by insulating gases having densities substantially higher than that of air or Where the medium is constituted by an insulating liquid.

It is also known that permanent magnets have been used and so disposed in the proximity of a direct cur: rent electric arc as to facilitate its extinction in air by causing its rapid displacement transversely to the magnetic field produced by the said magnets and its progressive increase in length until the conditions of arc instability are attained.

Similar permanent magnets have also been used in order to cause the rapid displacement of an alternating current electric are inside of extinguishing chambers constituted by narrow slots delimited, both laterally and posteriorly, by walls of insulating material capable of evolving abundant amounts of an arc extinguishing gas when heated by the direct action of the are on them. In such chambers the magnetic field produced by the permanent magnets placed along the lateral walls has a constant polarity and direction so that the transverse displacements of the alternating current electric arc in them take the form of an oscillatory motion which presents phases of motion having a direction contrary to the one desired for obtaining the rapid movement and extinction of the are under the action of the gases generated by the posterior wall of the chamber.

It will be understood that, within chambers of such type the interrupting time will be influenced both by the intensity and by the polarity of the current half-wave or loop which flows in the are at the instant of its initiation upon contact separation, and will therefore have different durations in the various opening operations. They are also not suitable for applications within high capacity circuit breakers where the presence of very heavy currents requires immediate initiation of the arc extinguishing action which must develop effectively without delay in order to obtain the shortest arc duration.

The above mentioned application of permanent magnets permits building are extinguishing chambers of low etficiency in connection with alternating current arcs because they produce a unilateral or single-sided action i.e. they exert their action for displacing the electric arc towards the means provided for causing its extinction only for the half-waves or loops of the alternating current having a certain polarity. The half-waves having the polarity opposite to the previous one will cause the arc to be driven by the constant magnetic field, produced by the permanent magnets, away from the extinguishing means or to remain between the open contacts until the next reversal of the half-wave polarity. In the presence of heavy currents which a circuit breaker may be required to interrupt promptly, such a performance may cause heavy thermic stresses, from the part of the electric are, which may impair the life of the interrupter active parts and produce ionizations of such high intensity within the medium surrounding the arc path as to surpass those permitting the successful and final extinction of the arc.

Another arrangement of permanent magnets already used for the extinction of alternating current arcs is constituted by two permanent magnets having the shape of cylinders and disposed with two ends of the same polarity facing one another. The radial field which is thus produced in the annular region interposed between the two magnets acts on the electric are drawn between two tubular contact members surrounding the magnets and moving coaxially with and alongside them. The are will displace itself in rapid rotational motion around the common axis of both the tubular contact members and the magnets, taking a clockwise or anticlockwise direction in relation to the polarity of the current half-wave flowing in the arc. Its length will be practically constant being fixed by the distance of the contacts which is limited by the spacing of the magnets. The immersion of said interrupter within an atmosphere of hydrogen facilitates the arc displacements due to the minimum density and viscosity of such a medium and permits to reduce substantially the intensity of the radial magnetic field required to set the arc in rapid mo tion. The result is the reduction of the magnet dimensions and consequently of the overall cost.

The effect of rapidly moving the are within the insulating medium is to favor its cooling and its deionisation in order to cause its extinction at the natural Zero value of the current. The limitation of the arc length fixed by the distance between the pole-faces of the magnets, which can not be more than a few centimeters in order to satisfy the requirements of the above magnetic circuit, in connection with the intensity of the radial field required to ensure the efiicient action on the are for the whole range of currents to be interrupted, establishes also a relatively low limit for the voltage of the circuits which may be interrupted by devices of such a type.

Accordingly, one object of this invention is to provide an improved arc extinguishing chamber for alternating current capable of exerting on the are a bilateral action obtained by the use of couples of permanent magnets producing one or more constant magnetic fields conveniently disposed and of proper strength for providing a prompt and efficient driving action on the alternating current electric arc, which is drawn upon separation of the contacts of an interrupting device, transversely to the magnetic field or fields. By this action, the arc will be displaced and forced to enter either one of the two sections of an extinguishing chamber, each section being provided for acting efliciently on a different polarity of the half-waves or loops of the alternating current, in order to force the arc to increase its length, under the effect of magnetic fields also produced by couples of permanent magnets conveniently conformed and disposed, to rapidly reduce its temperature and deionise itself until its final extinction at the instant the current goes through its natural Zero value. The magnetic fields must possess high flux densities, i.e. in the order of 0.1 Weber/m. or more, in order to act efiiciently for displacing promptly the electric arc towards the interior of either section of the extinguishing chamber, especially where the medium within which the chamber is immersed is constituted by a high density gas or by an insulating liquid. This invention provides, to this effect, appropriate return circuits for the magnetic flux of each couple of permanent magnets facing one another, made of materials having good magnetic permeability in order to secure the highest possible density for the magnetic flux in the region between the polar faces of each of the couples. The promptness and the speed of the motion impressed upon the electric arc inside the extinguishing chamber from the instant of its initiation permit the chamher to withstand heavy currents and to be suitable for use in connection with alternating current circuit breakers for voltages of relatively high values. The ambient, within which the electric arc is drawn and the chamber is placed, is constituted by a space which is insulating in relation to electrical phenomena and can be filled either with air or an insulating gas such as hydrogen, sulphur hexafluoride, or any other gas having physical properties similar to those of the latter, or with mixtures of such gases together with air. The space may be filled with an insulating liquid such as water, oil, or any other liquid having appropriate physical and chemical properties such as, for example, liquid sulfur hexafiuoride. Finally it may also be constituted by a space where any convenient degree of vacuum can be obtained and preserved for reasonable lengths of time.

The presence of high intensity magnetic fields within the regions of probable reignition of the electric arc, after the current has gone through its natural zero value, besides ensuring the continuous permanence of an efficie'nt action tending to displace promptly the electric arc towards the means provided for accomplishing its extinction for all values, including the smallest ones, of the current to be interrupted, increases, as it is Well known, the value of the recovery voltage required to cause arc reignition and improves consequently the resistance of the insulating medium against resumption of the are discharge. This represents an important advantage of the permanent magnets fields over those produced by electromagnets energized by the same current of the circuit to be interrupted, because these latter fields will collapse to Zero intensity when the alternating current goes through its natural zero value, and will not be able to contribute to the improvement of the dielectric resistance of the medium surrounding the arc.

Means adapted for delaying the immediate and total collapsing of the magnetic fields produced by the electromagnets when the current of the circuit goes through its zero value can be provided. They may be constituted, for example, by shading coils of conducting material which, being short-circuited and wound around the cores of the electromagnets producing the fields, will have currents induced in their conductors during the phases of field collapsing. The action of such induced currents is to shift the phase of the main field in relation to the current so as to delay the prompt and total collapsing of the main field and hold a residual field within the region located between the electromagnet polar faces during the time the current to be interrupted goes through its natural zero-value.

The duration and the intensity of such residual field have a relatively limited effect while the means used entail considerable complications in design of the electromagnets structure, the cost of which may be justified only for breakers having high interrupting ratings.

A further object of this invention is to form each section, of the extinguishing chamber for alternating current arcs in the shape of a labyrinth in order to force the electric arc to follow paths having the shape of zig-zag lines between walls, made of refractory ceramic insulating materials able to resist the direct action of electric arcs, which delimit narrow slots within which act transverse magnetic fields produced by permanent magnets conveniently disposed behind said walls. The electric are, after entering one section of the extinguishing chamber, will be subjected along its entire length, without any limitation due to the distance between the permanent magnet pole faces, to forces displacing it rapidly within the said confining slots and along their respective walls until it will extinguish itself at the instant the alternating current flowing through it goes through its natural zero value.

Another object of this invention is to dispose two consecutive sections of opposite polarities on each side of the path followed by the alternating current electric are, which is drawn upon separation of the contacts of an interrupting device, for the purpose of providing an eflicient action of the extinguishing chamber. This is particularly effective for circuits having voltage and inductance characteristics which will not permit extinguishing the arc at the first zero value of the current to be interrupted.

Means are provided to ensure the stability of the permanent magnets used within any of the above mentioned chambers and protect them against the demagnetizing actions produced by the electric arc, namely:

(a) Thermic action of the electric arc column on the insulating walls of ceramic material coming in close proximity with it. Such action causes heating of said walls and successively of the parts located immediately behind them. It is well known that the magnetic strength of metalloids, oxides and ferrite permanent magnets is influenced by temperature and is subjected to losses which are reversible only when the maximum temperature of approximately 350, corresponding to the Curie point, is not reached by the magnets;

(b) Magnetic action of the current flowing in the electric arc which produces in the surrounding space a magnetic field which opposes the one produced by the permanent magnets for the region towards which the said arc is being displaced. This demagnetizing action will be particularly strong when the chamber is handling very intense currents.

Appropriate means may be used in the form of convenient polar shoes, made of a material having good magnetic permeability and interposed between the insulating walls and the permanent magnet surfaces, so shaped as to conduct the magnetic fluxes produced by the magnets to act on the arc column unaltered with respect to both their strength and zone of action.

Such polar shoes will permit increasing the permanent magnet spacing from the heated insulating walls and creating magnetic shields for the magnets, as they constitute convenient return circuits for the demagnetizing flux produced by the current flowing in the arc.

The above described objects and advantages of this invention, together with the other ones obtained by the application of the principle indicated above, will become more apparent upon consideration of the following detailed description of preferred forms of embodiment thereof, when taken in connection with the accompanying drawings which are shown only for the purpose of illustration and will not constitute any limitation of the scope of this invention:

FIG. 1 shows schematically the longitudinal cross sectional view of an arc extinguishing chamber for alternating current capable of a bilateral action on the electric arc and constituted by two sections, each section being formed by two permanent magnets of opposite polarities and protected by insulating materials capable of resisting the direct action of the electric arc.

FIG. 2 shows a cross sectional view through the arc extinguishing chamber substantially on the line A-A of FIG. 1.

FIG. 3 shows a horizontal sectional view of the arc extinguishing chamber of FIG. 1.

FIG. 4 and FIG. 5 show, respectively, the longitudinal cross sectional view and the top view of an arc extinguishing chamber for alternating current capable of a double bilateral action on the electric arc and constituted by four sections, each section being formed by two permanent magnets of opposite polarities and protected by insulating materials capable of resisting the direct action of the electric arc.

FIGS. 6 and 7 show schematically the cross sectional views substantially on the lines BB and C-C, of FIG- URES 4 and 5, respectively.

FIG. 8 shows a side elevation View, having a portion in cross sectional view substantially on the line FF of FIG. 9, of another form of embodiment of an are extinguishing chamber for alternating current capable of a bilateral action on the electric arc and constituted by two sections, each section provided with systems of permanent magnets of opposite polarities conveniently supported and disposed.

FIG. 9 shows the cross sectional view substantially along the line DD of FIGURES 8 and 11.

FIGS. 10 and 11 show more in detail two horizontal sectional views of a part of an extinguishing chamber of the type shown in FIGS. 8 and 9. More particularly, FIG. 10 shows the cross sectional view substantially on the line GG of FIG. 9, while FIG. 11 shows the cross sectional view substantially on the line E-E of the same FIG. 9.

FIG. 12 shows a perspective view of an extinguishing chamber similar to the one shown in FIGURES 1 to 3 but having the two couples of permanent magnets provided with magnetic return circuits for the magnetic flux they produce.

FIG. 13 shows an exploded perspective view of a part of the upper section of the extinguishing chamber shown on FIGURES 8, 9, 10 and 11, where only the electric and magnetic active parts have been represented.

FIG. 14 illustrates schematically an alternate solution for protecting the stability of the permanent magnets used in arc extinguishing chambers made in accordance with this invention and particularly adapted for those used in the chamber embodiment illustrated in FIGS. 8, 9, l0 and 11.

FIG. 15 illustrates schematically another alternate solution for protecting the stability of the permanent magnets used in arc extinguishing chambers made in accordance with this invention and particularly adapted for those used in the chamber embodiments illustrated in 'FIGS. 1 to 7 and 12.

FIGS. 16, 17 and 18 show schematically and respectively a vertical cross sectional view, a top view and a longitudinal cross sectional view, substantially on the line X-Y of FIG. 16, of an alternate embodiment of the transversal magnetic system particularly adpated for the extinguishing chamber illustrated in FIGURES 8, 9, 10 and 11.

FIGS. 19, 20 and 21 show schematically and respectively a vertical cross sectional view, a top view and a longitudinal cross sectional view, substantially on the line V-W of FIG. 19, of another alternate and simplified embodiment of the transversal magnetic system particularly adapted for theextinguishing chambers illustrated in FIG- URES 8, 9,10 and 11.

Referring to the drawings and particularly to FIG- URES l, 2 and 3 thereof, I have shown an embodiment of the invention where the arc extinguishing chamber, comprising two sections, is constituted by an envelope of insulating material formed by the end walls 3 and side walls 4 supporting, in any convenient way, the two couples of permanent magnets 5-6 and 7-8 which constitute the upper and lower sections of the said chamber, respectively, and are symmetrically disposed in relation to the contacts 1 and 2 of the circuit interrupter incorporating the arc extinguishing chamber. In this case the permanent magnets are preferably made of mixed metalloid oxide compounds and ferrite, i.e. of magnetic materials having high electrical resistivity and suitable to be easily formed by pressing with mechanical means. The shape given to them, in this case, is such as to create a duct 10 for the passage of the movable contact 2 in the central part of the chamber. The remaining part of each magnet inner surface is provided with protruding ridges substantially perpendicularly disposed with respect to the central duct 10 and having higher elevations towards the upper and lower ends, respectively, so combined as to create, between the ridges of the magnets of each couple 5-6 and 7-8, narrow slots which constitute a zig-zag confining path of increasing length for the electric arc. Such confining slots have been designated 11 and 12, respectively, on FIGURES 1, 2 and 3 whereas their shape is clearly shown in FIG. 3.

The polarity of the magnets faces is indicated with the letter N for the north polarity and with the letter S for the south polarity. They are thus suitable to produce constant magnetic fields transversely of the slots 11 and 12 separating them.

The surfaces of the permanent magnets adjacent to the slots 11 and 12 are protected by plates 13 of refractory ceramic insulating material capable of resisting the direct action of the electric arc. If convenient, the magnets may be formed of non conductive materials, as mixed metalloid oxide compounds and ferrite, in which event the plates 13 of ceramic insulating material may be dispensed with. Such plates have been shown also in FIGURES 2 and 3 in order to illustrate their conformation and disposition.

At the time of an opening operation of the interrupting apparatus, to which the arc extinguishing chamber is applied, the movable contact 2 separates itself from the stationary contact 1, passing inside the duct or path of travel existing in the central part of the extinguishing chamber. The electric arc, which is drawn between the contacts, is subjected to the transverse magnetic field produced by the couples of magnets 5-6 and 7-8 and is forced to displace itself towards the upper seciton of the extinguishing chamber, as indicated for example by the line 14, if the current half-wave or loop flowing in the are at the instant of contact separation is directed from contact 2 to contact 1. The are will instead displace itself towards the lower section if the current half-wave or loop is directed from contact 1 to contact 2.

The action of the magnetic field on the arc is continuous and exerts itself along the whole arc length in order to displace it rapidly towards the interior of the proper section, within a zig-zag confining path increasing its length and causing its cooling in contact with the slot walls. The strong deionisation which will thus be accomplished will cause the extinction of the arc at the instant the current passes through its natural zero value. The deionisation of the insulating medium surrounding the arc region, and the presence of the permanent magnetic field, will increase the value of the voltage necessary for the reignition of the arc, generally above the recovery voltage appearing across the contacts 1 and 2 at the time the current flowing in the arc will extinguish itself by passing through its natural zero value. In such condition, the electrical circuit connected to the contacts will be positively interrupted.

Turning to FIGURES 4 to 7 of the drawings, there is illustrated a form of embodiment represented by an arc extinguishing chamber constituted by the four sections M, O and P, Q, ie., by four couples of permanent magnet sections practically identical With those shown on FIGURES l to 3 but having the polarities of the magnets belonging to the second sections, P and Q, reversed in respect to those of the corresponding magnets belonging to the first sections, M and O.

This type of arc extinguishing chamber is specially suitable for the interruption of electric circuits requiring a longer contacts breaking distance due to the presence of higher voltages or of higher inductance in the circuits.

The extinguishing chamber is constituted, also in this case, by an envelope of insulating materials comprising the end walls 23, 23' and side walls 24 which support, in any convenient way, the couples of permanent magnets 25-26 and 27-28, constituting the two sections M and 0, respectively, together with the couples of permanent magnets 25-26' and 27-28' constituting the two sections P and Q, respectively, of the same chamber. The

shape given to the permanent magnets is also in this case such as to create a duct 30, for the passage of the movable contact 22, in the central part of the chamber. The remaining part of each magnet inner surface is provided with protruding ridges substantially perpendicularly disposed with respect to the said central duct and having higher elevations towards the upper and lower ends, re-

spectively, so combined as to create, between the ridges of the coupled magnets, the narrow slots 31-32 and 31'- 32, constituting zig-zag confining paths of increasing length for the electric arc.

The polarity of the magnet polar faces is indicated in FIGURES 5, 6 and 7 with the letter N for the north polarity and with the letter S for the south polarity. They are thus suitable to produce constant magnetic fields transversely of the slots 31-32 and 31'32' separating them.

The surfaces of the permanent magnets adjacent to the slots 31-32 and 31-32 can be protected, if necessary, by plates 33 of refractory ceramic insulating material capable of resisting the direct action of the electric arc.

At the time of an opening operation, the movable contact 22 separates itself from the stationary contact 21, passing inside the duct 30 existing in the central part of the extinguishing chamber. The electric are which is drawn between the contacts is subjected to the transverse magnetic fields produced by the couples of permanent magnets and is forced to displace itself towards the upper section M of the extinguishing chamber along the path comprised within magnets 25-26, as indicated, for example, by reference 34', and consecutively towards the lower section Q of the chamber along the path comprised within magnets 27'-28', as indicated, for example, by reference 34, if the current half-wave or loop flowing in the arc at the instant of contact separation is directed from contact 22 to contact 21. The arc will instead displace itself towards the lower section 0 of the chamber along the path comprised within magnets 27-28 and consecutively towards the upper section P of the chamber along the path comprised between magnets 25-26 if the current half-wave or loop flowing in the arc is directed from contact 21 to contact 22.

In FIG. 4, each line 34-34 represents one of the instantaneous positions the electric arc will assume Within the chamber for a current half-wave or loop directed from contact 22 to contact 21.

The action of the magnetic fields on the arc is continuous and exerts itself, as in the case of FIG. 1, in a similar Way along the whole length of the arc in order to displace it rapidly for increasing its length, its cooling and deionisation so as to cause its extinction at the instant the current passes through its zero value.

As a difference from the chamber illustrated by FIG- URES 1 to 3, the one illustrated by FIGURES 4 to 7 makes it possible to reduce, for the same total length of the arc, the depth of its penetration inside the sections of the chamber and consequently the height of the sections.

According to what has been already said above, this type of extinguishing chamber is also suitable for the interruption of electric circuits requiring a longer contacts breaking distance. The distance reached by the movable contact within the time corresponding to one half cycle of the alternating current to be interrupted, which is required in order to ensure the current passing through the zero value may be insufficient for obtaining the final extinction of the arc, which may thus reignite between the contacts and require a further action of the extinguishing chamber that this time will exert itself on a freater length of the arc. The advantage of reducing, by using this type of chamber, the depth of penetration of the are inside the depth of penetration of the arc inside the sections of the chamber and consequently the height of the same sections is evident.

The strength of the magnetic fields produced within the slots existing between the couples of permanent magnets constituting each section, as the slots indicated by references 11, 12, 31-32 and 31'-32', can be increased substantially by providing appropriate return circuits for the magnetic flux produced by each couple of said permanent magnets.

Accordingly, FIG. 12 shows schematically a perspective view of anextinguishing chamber similar to the type illustrated by FIGURES 1 to 3. In FIG. 12, the component parts corresponding to those of FIGURES 1 to 3 have been marked with the same reference characters.

The references 1 and 2 represent schematically the fixed and movable contacts, respectively, of the inter- 'rupting apparatus incorporating the arc extinguishing chamber, 5 and 6 are the permanent magnets constituting the upper section of the chamber and having their opposing polar surfaces provided with protruding ridges substantially perpendicularly disposed with respect to the central duct 10 and of increasing elevations towards the upper and lower ends, respectively, and so combined as to create, between the ridges of the coupled magnets, the narrow confining slots 11 inside which is attracted the electric are initiated upon separation of contacts 1 and 2 and drawn by contact 2 moving inside the duct 10 existing among magnets 5-6 and 7-8. Magnets 7-8 constitute the lower section of the extinction chamber and are perfectly similar and symmetrical to those indicated as 5-6.

Reference characters 66-67 in FIGURE 12 designate the return circuits for the magnetic fluxes of the couples of magnets 5-6 and 7-8, respectively. Such return circuits, which preferably have the shape shown on the drawing, are advantageously constituted, totally or partially, of a magnetic material having high electrical resistivity. The application of such return circuits to the magnets is extremely simple and easy, and it permits increasing substantially the intensity of the fields across the slots, such as the one marked with reference 11, inside which the are is attracted and confined, in order to expedite its extinction.

The detailed description of the performance of this arc extinguishing chamber will not be given as such performance is identical with that of the chamber illustrated by FIGURES 1 to 3. Turning to FIGS. 8, 9, 10 and 11 of the drawings, there is illustrated a form of embodiment represented by an arc extinguishing chamber comprising a larger number of permanent magnet couples for each section and using a number of elementary permanent magnets, preferably provided with magnetic return circuits, so that this type of chamber, on account of the number and disposition of the permanent magnet couples and also of the high intensity of the magnetic fields they produce, is capable of interrupting electric arcs carrying currents of very high intensities.

{is appears more clearly from FIGS. 8 and 9, the arc extinguishing chamber is constituted by an envelope of insulating material comprising end walls 43 and longitudinal walls 44 which support, together with the transverse insulating plates 59, the assemblies of permanent magnets 45-46, 55-56, 57-58, and 47-48, 53-54, 57-58 whlch constitute substantially the upper and lower sectlons of the said chamber, respectively. The disposition of the magnet assemblies and the shape given to the pairs of insulating plates 59 which, together with insulating members 59, protect and support the assemblies, are such as to create a duct 50 for the passage of the movable contact 42 when it separates from the stationary contact 41.

Such type of extinction chamber, comprises in each section, besides the permanent magnets disposed, as in the previously described chambers, along the arc path, also two couples of permanent magnets 45-46 and 47-48, respectively, located with-in the zone where the separation of the movable contact 42 from the stationary contact 41 takes place. The function of such two couples 45-46 and 47-48 is to produce a strong magnetic field acting transversely of the direction of the contact movement and capable of causing the rapid displacement of the alternating current electric are, which is drawn between the contacts at the instant of their separation, towards the inner part of either one of the two sections constituting the extinction chamber, according to the direction of the current half-wave or loop flowing in the are at that instant.

10 Such permanent magnets are protected against the direct action of the electric arc, which develops in the proximity of their polar faces, by the insulating plates 64 of refractory ceramic material shown by dotted lines in FIG. 8.

In order to ensure the maximum intensity for the magnetic fields produced by the couples of permanent magnets, 45-46 and 47-48, respective return circuits are provided for the fluxes they produce as indicated on the drawings at 49 and 39, each return member 49' and 39 being made with a material having a good magnetic permeability and formed so as to embrace the rear end of the chamber for constituting the shortest return circuits for the fluxes of the couples 45-46 and 47-48, respectively.

In correspondence with stationary contact 41, two conducting plates 51 and 52 are disposed and connected electrically, in any convenient way, to contact 41 so as to constitute two guiding horns for the root of the electric are which will thus be able to travel along either one of said plates which are made of any suitable conducting material such as, for example, copper or the like.

The remaining couples of magnets 53-54 and 55-56 (see FIG. 10*) are made of elementary permanent magnets with the former disposed inside the lower section, and the latter disposed inside the upper section, as clearly shown on FIG. 9 which illustrates a cross-sectional view of this type of chamber. They are disposed along the duct 50, corresponding to the path followed by the movable contact 42, for the purpose of producing within the central zone of the chamber, where the movable contact travels, transverse magnetic fields having the same polarity as those produced by the couples of magnets 45-46 and 47-48 so as to favor the displacement of the electric arc in the same direction. The magnets polarities have been indicated also in this case, and as usual, with N for the north polarity and with S for the south polarity, respectively. All these couples of permanent magnets or a part of them can be provided with appropriate return circuits for the fluxes they produce.

Each section of this chamber comprises also other couples of permanent magnets, namely those indicated at 57, 58 and 57', 58' in FIGS. 8 and 11. These latter couples of permanent magnets are supported, as it has already been said, by the transverse insulating plates 59 and the longitudinal walls 44, such transverse plates having shapes and dispositions such as to create (see FIGURES 8 and 11) between themselves narrow slots 61 which are in spaced parallel relation and perpendicular to duct 50. Slots or gaps 61 form, together with the passages provided alongside and parallel to the side walls 44 of the chambers, a labyrinth confining path similar to the one indicated by the dotted line 62 in FIG. 11 and capable of causing a rapid and substantial elongation of the electric are when the latter is displacing itself towards the inner part of the extinguishing chamber section.

The elementary permanent magnets 57-58 and 57'-5=8 which, together with their magnetic return circuits 63, are supported by plates 59 and walls 44, have the function of producing magnetic fields directed transversely of the slots 61, constituted by the clearances existing between the adjacent couples of plates 59, such fields being capable of accelerating the displacement of the electric are previously initiated towards the inner part of the extinguishing chamber respective section.

The line 62 in FIG. 8 shows, in a longitudinal projection, the shape of an instantaneous position presumably taken by the electric are drawn between contacts 41 and 42, while line 62 in FIG. 11 shows the shape taken by the arc, practically at the same instant, as seen from the top.

The longitudinal walls 44 of the extinguishing chamber under consideration are preferably protected by plates 60 Which, similarly to the transverse plates 59, are made of refractory ceramic insulating material capable of resisting the direct action of the electric arc.

As it has already been mentioned, the disposition of the consecutive couples of transverse plates 59, within each section of the chamber, is such as to present trapezoidal shaped central openings between the plates of the two sections, which are clearly visible in FIG. 9, and which extend alternately to the right and to the left so as to create between the plates a labyrinth path for the arc when the latter is forced to enter it under the action of the magnetic fields. Such labyrinth is constituted mainly by the slots 61, and is clearly visible in FIG. 11.

In order to obtain the maximum effect from the permanent magnets 57-58 as well as from the identical magnets 57'58", appropriate magnetic return circuits 63 are provided for each couple of said magnets, such return circuits being partially or totally constituted by plates conveniently shaped or bent and of materials having good magnetic permeability together with good insulating properties. Materials of such kind are known to be oxides of metalloids, as for example barium oxides, mixed with suitable magnetic ferrites making a mixture adapted to forming by sintering.

The understanding of the structure and performance of such type of arc extinguishing chamber will be better effected by considering FIG. 13, which shows an exploded prospective view of the upper section of the arc extinguishing chamber illustrated in FIGS. 8, 9, 10 and 11.

For the sake of obtaining a clearer and simpler drawing, only the significant electrical and magnetic parts of this section of the extinguishing chamber have been represented. The supporting walls, the refractory ceramic insulating transversal plates and protective members have not been represented. The corresponding parts have been marked with the same reference characters as used for FIGURES 8, 9, l and 11. Thus the reference characters 41 and 42 indicate, respectively, the stationary and movable contacts of the interrupting device incorporating the arc extinguishing chamber. Reference character 51 indicates the conducting plate of the upper section electrically connected to the stationary contact 41 and constituting one of the guiding horns for the rapid displacement of the arc root provided for contact 41. On this figure has been also shown the flexible electrical connection 65 between the plate 51 and the contact 41.

Reference character 45 indicates one of the two permanent magnets located in the upper section of the chamber and disposed in the proximity of the Zone where the contacts separation occurs. The companion magnet 46, coupled with it, has been shown by dotted lines because FIG. 13 shows only part of the components of the upper chamber section being considered.

FIG. 13 shows clearly the various elements which, 8

together with the transverse refractory ceramic insulating plates not shown on this figure, define the path provided for the arc. Such elements, or magnetic systems, which are shown distances from one another larger than in the real case, comprise each a couple of elementary permanent magnets 57-57 and -5858 which produce, across the various sections of the slots 61 constituting the labyrinth path for the arc, magnetic fields capable of accelerating the displacement of the arc towards the inner part of the chamber section. Each couple of magnets is provided. with a return circuit 63 for its magnetic flux, as clearly shown in FIG. 13 together with the shape and disposition of both the elementary magnets 57 and 58 and the parts constituting the return circuit 63, which, also in this case, can be totally or partially very conveniently constituted by materials having good magnetic permeability together with high electrical resistivity.

The line 62 shows schematically one of the instantaneous positions the arc, drawn between the contacts 41 and 42 upon their separation, will take during its displacement towards the upper and inner ends of the extinguishing chamber sections, on the assumption that the halfwave or loop of the current flowing in the arc is directed from contact 42 to contact 41. In FIG. 13, it is shown that the arc root 62', which at the instant of contact separation impinged on contact 41, has already displaced itself along plate 51 connected by means of the conducting connection 65 to contact 41.

In FIG. 13, the couples of elementary permanent magnets, which are disposed along the path of the movable contact 42 and marked with reference characters 55 and 56 in FIGURES 9 and 10, have not been drawn for the sake of simplicity.

The operation of an arc extinguishing chamber such as the one illustrated in FIGURES 8 to 11 is as follows: upon each opening of the contacts, the movable contact 42 separates from the stationary contact 41, passing inside the duct 50 in the central part of the chamber. During the instants immediately preceding such contact separation, the current flowing in the circuit to be interrupted is already subjected to the action of the magnetic field produced by the magnets 4546 and 47-48 transversely of the direction of contact motion, so that the current will tend to dispose itself towards the upper edges of the conductors constituting the contacts if the half-wave or loop of the current is directed, as in FIG. 8, from contact 42 to contact 41.

At the instant of contact separation the root of the are which is initiated will already impinge on the contact edge located in the proximity of the guiding horn 51, and will start its displacement along such horn, without delay, under the action exerted by the transverse magnetic field produced by magnets 45-46.

Such displacement of the arc root brings the arc to contact the slanting edges of the couples of transverse refractory ceramic insulating plates '59 and to enter, bending itself along such plates, the confining slots or air gaps 61 where it Will be subjected to the magnetic fields produced transversely of said slots 61 by permanent magnets 57 and 58. The action of such fields exerts itself, evidently, on the major part of the arc length and causes its rapid elongation within the labyrinth formed by the slots 61 and the edges of the plates 59. This will also produce a rapid cooling and a strong deionisation of the arc which will thus be extinguished at the instant the current passes through its zero value.

A similar performance, but with the displacement direction of the are reversed, i.e., towards the lower section of the extinguishing chamber, will take place when the half-wave or loop of the current existing at the instant of contact separation is also reversed with respect to the preceding one and is directed from contact 41 to contact 42.

When describing the performance of the extinguishing chamber illustrated by FIGURES 8 to 11 it has been assumed, up to this point, that the duration of the current half-wave or loop, presenting itself at the instant of contact separation, would be suflicient to allow the electric are it produces to enter deeply within either section of the chamber before the current passes through its first zero value. If, instead, the contact separation takes place at an instant corresponding to the descending quadrant of a half wave, i.e. at an instant not sufliciently far from the one when the current passes through its first zero value,.the action exerted by the section of the chamber having the proper magnetic fields capable of attracting the are inside its own labyrinth may have, in some cases, a duration not suflicient to obtain the immediate final extinction of the said arc. An effective action will then be exerted by the other section of the same chamber on the successive current half-wave flowing in the reignitedarc and having a sufficient duration to permit the arc to be attracted and driven to enter the inner part of the section, while the movable contact will have reached, in the meantime, a distance from the stationary one sufiicient to pre vent a new reignition of the arc after its extinction.

It is readily understood that, also with the type of arc extinguishing chamber illustrated by FIGURES 8 to 11, the sections can be instead of two, as considered. up

1 13 to this point, four as explained in the case covered by FIGURES 4 to 7 or a greater number, provided each consecutive section will have the polarities of its magnetic fields reversed with respect to those of the preceding section, by properly disposing the respective permanent magnets 53-54, 55-56, 5758 and 57'58'.

Turning to FIG. 14 of the drawings, there is illustrated schematically an alternate solution for protecting the permanent magnets, used in arc extinguishing chambers of the types illustrated in FIGURES 8, 9, 10, 11 and 13,- against the demagnetizing actions of the electric arc. According to such solution, polar shoes, made of mild steel or of any material having good magnetic permeability, are interposed between the facing polar surface of the permanent magnets and the refractory ceramic insulating walls, disposed in close proximity with them, for the purpose of protecting the magnets from the demagnetizing actions of the electric arc.

Such demagnetizing actions mainly arise from two causes, namely:

(a) The thermic effect of the electric are on the walls adjacent the path in which it develops, resulting in severe heating of the walls and consequently of the permanent magnets disposed behind them but in close proximity with them;

(b) The magnetic field generated by the electric current flowing in the electric are that establishes a magnetic flux in the surrounding space which, within the region located where the displacement of the arc is directed, has a signcontrary to that of the flux generated by the permanent magnets disposed along the arc path in order to displace the arc towards the inner part of the chamber section. Such action can be particularly strong for the more intense currents which the chamber may be called to interrupt.

The polar shoes, provided in accordance with the alternate solution illustrated in FIG. 14, have a shape and thickness adapted for carrying the constant magnetic flux, generated by the said permanent magnets, to the convenient zone and points where it can act on the are as desired although avoiding any direct contact of the permanent magnets with the wall surfaces which, being disposed in close proximity with the arc column, may attain in certain cases very high temperatures.

In FIG. 14 the permanent magnets 70 and 71, incorporated in an arc extinguishing chamber embodying this invention, are provided with a return circuit 74 for the magnetic flux they produce together when disposed with their polar faces of opposite polarity facing one another. The refractory ceramic insulating walls 68 and 69 correspond to the walls 59 and 64 of FIGURES 8 to 11 and protect the magnets from the direct action of the electric are 62. In addition, polar shoes 72 and 73 are interposed between each permanent magnet and the refractory ceramic walls. Such polar shoes are preferably made of metallic materials having good magnetic permeability, such as mild steel or the like, but in' some cases they can be also made of non-metallic materials having good magnetic permeability together with high electrical resistivity.

' It will be clearly understood, particularly by those skilled in the art, that the functions of such polar shoes are mainly three.

The first one'is to permit disposing the permanent magnets at a greater distance from the arc zone without altering appreciably the effective length of the magnetic system air gap and the intensity of the magnetic flux produced by the permanent magnets across the path where the electric arc develops.

The second one is to eliminate the intimate contact of the permanent magnets with the ceramic plates, which latter may attain very high temperatures when intense currents flow in the electric arcs they contact.

The third function is to provide a path of high permeability for the magnetic field produced by the currents flowing in the are, so as to obtain an effective shielding of the permanent magnets 70 and 71 disposed behind them.

It is evident to those skilled in the art that such polar shoes are easy applied, when necessary, to any of the couples of permanent magnets incorporated within any of the arc extinguishing chambers described above. In some cases it will be more convenient to subdivide the polar shoes in separate sections or segments having their longer dimension disposed perpendicularly to the axis of the arc, so as to create the desired paths for the magnetic field produced by the current flowing in the arc without impairing the insulating properties of the members adjacent to the arc path, beyond the acceptable limits.

Accordingly, FIG. 15 illustrates another alternate solution wherein are considered subdivided polar shoes as applicable more particularl to the embodiments of extinguishing chamber shown in FIGS. 1, 2, 3, 4, 5, 6, 7 and 12. The same reference characters as used in FIG. 14, but marked with a prime, have been employed to designate the corresponding parts having the same functions in the alternate solution of the polar shoes application.

The permanent magnets 70 and 71, incorporated in an arc extinguishing chamber embodying this invention, are provided with a return circuit 74 for the magnetic flux they produce together when disposed with their polar faces of opposite polarity facing one another. The refractory ceramic walls 68' and 69' protect the magnets from the direct action of the electric are developing within the zig-zag path determined by the walls. In addition, separate polar segments 72 and 73', of appropriate shapes, are interposed between each permanent magnet and the ceramic walls 68' and 69'.

Such polar shoes segments are preferably made of metallic materials having good magnetic permeability, such as mild steel or the like, but in the cases where the distances separating the segments will not be suflicient to ensure the insulating characteristics required for the satisfactory operation of the extinguishing chamber, the polar shoes segments can also be made, totally or partially, of non metallic materials having good magnetic permeability together with high electric resistivity.

The disposition of both the permanent magnets couples and the relative magnetic return circuits, constituting the transverse magnetic systems used within the sections of the arc extinguishing chamber illustrated in FIGS. 8 to 11 and 13, can be accomplished in different ways without altering the principle of operation materialized by the embodiment of arc extinguishing chamber already described.

Accordingly, FIGS. 16 to 21 of the drawings show, for example, the alternate solution for the transverse magnetic systems capable of obtaining either magnetic fields of higher intensities or structural simplifications, together with the possibility of removing entirely the permanent magnets from the demagnetizing actions of the electric arc.

Turning to FIGS. 16, 17 and 18 of the drawings, there are illustrated more particularly some modifications of the return circuits, designated by reference character 63 in FIGS. 8 to 11 and 13, which makes it possible to use simplier shapes for the component parts of the return circuits and, if desired, the interposition of additional permanent magnets disposed externally to the insulating envelope enclosing the arc extinguishing chamber proper. The plate 63", made of a material having good magnetic permeability, are disposed directly behind the permanent magnets 57, constituting one transverse couple. These plates are of a flat shape, also for the portions projecting externally beyond the longitudinal Walls 44 of the insulating envelope (see FIG. 17), and embrace the prismatic blocks 75. These blocks complete the return circuit for the magnetic flux produced by the magnets couple as they are made of a material having good magnetic permeability together with a high electric resistivity,

15 in order to ensure also good longitudinal electrical insluation of the arc extinguishing chamber.

In some cases it may prove convenient to use permanent magnets instead of the prismatic blocks 75, such permanent magnets being constituted of non metallic materials of the group metalloid oxides and ferrites and properly polarized in order to contribute to the substantial increase of the total magnetic strength of the magnetic system of which they are a part. 7

FIGS. 17 and 18 show also the polar shoes 72 and 73", having the function of ensuring a better stability of the permanent magnets 57 by protecting them against the demagnetizing actions of the electric arc, as well as the insulating wrapping or tube 7 8 having the purpose of binding solidly together all the components of one transverse system assembled in the chamber sections, including also the refractory ceramic insulating plates 59 and their related insulating spacers 79.

FIGURES 16 and 18 show also the insulating shields 77 provided for protecting the edges of the polar shoes 72" and 73" together with the edges of the return circuits 63" in the cases Where the latter are made of mild steel or any similar magnetic material having low electric resistivity. In other cases, if desired, the polar shoes 72 and 73" together with the return circuits 63" may be made of non metallic materials having good magnetic permeability together with high electric resistivity, in which event such insulating shields may be dispensed with.

Turning to FIGS. 19, 20 and 21 of the drawings there are illustrated more particularly some structural simplificatlons of the above transverse magnetic system, wherein the use of only the external permanent magnets 75, together with the flat shaped plates 76, for carrying the magnetic flux to the arc extinguishing chamber region Where the electric arc develops, makes it possible to remove entirely the permanent magnets from the demagnetizing action of the electric arc. In other words, the plates 76 acquired have here the function of polar extenslons for the permanent magnets 75, disposed externally -of the extinguishing chamber, and are equally capable of carrying the magnetic flux produced by these magnets to act across the slots 61 constituting the labyrinth confining path provided for the electric arc.

FIGS. 19 and 21 show also the insulating shields 77 provided for protecting the edges of the plates 76 in the cases where they are made of mild steel or any similar magnetic material having low electric resistivity. In other cases, if desired, the polar extension plates 76 may be made of a non-metallic material having good magnetic permeability together with high electric resistivity, in which event such insulating shields may be dispensed with. The insulating wrapping or tube 78 is used here also, for binding solidly together all the components of one transverse magnetic system assembled in the chamber sections, including also the refractory ceramic insulating plates 59 and their related insulating spacers 79.

Results similar to those obtained by means of the above described modifications applying to the transverse magnetic systems used within the arc extinguishing chamber embodiments illustrated in FIGS. 8 to 11 and 13 may be obtained also for the longitudinal magnetic systems used within all the arc extinguishing chambers embodying this invention by inserting, within the external part of the magnetic return circuit of each couple of permanent magnets disposed on the sides of the interrupting apparatus contacts, one or more sections constituted by permanent magnets conveniently shaped and disposed so as to contribute to the substantial increase of the strength of the magnetic fields produced within the region of the arc extinguishing chamber wherein the electric arc will develop. Such additional sections of permanent magnets are preferably disposed externally of the walls of the extinguishing chamber so as to remove them entirely from the demagnetizing actions of the electric are developing within the chamber. In this event, the adidtional permanent magnets likewise may be constituted of metallic alloys having superior magnetic properties in comparison with those pertaining to the non-metallic permanent magnets constituted of met-alloid oxides and ferrites as indicated in the previous examples covering transverse magnetic systems. This will make it possible, if desired, to obtain very high intensities for the magnetic fields produced within the region of the arc extinguishing chamber wherein the electric arc will develop.

It has to be noted that in all the forms of embodiment of the arc extinguishing chambers, either of the above described types or of any other type different from those herein illustrated but still covered by this invention, the disposition of the sections is such as to obtain the prompt action of the chamber over the whole length of the developing electric arc and without leaving any appreciable part of it free, ie not subjected to the action purposely predisposed for causing its extinction.

It is also evident that are extinguishing chambers of the types as described above, or covered in any way by the scope of this invention, can be disposed at all points of a circuit where contact separations may occur simultaneously or successively and will in all cases ensure eflicient arc extinguishing action.

The extinguishing chambers embodying this invention lend themselves to be constructed for handling electric 'arcs having very different intensities, from relatively modest ones to very high ones, because, by selecting the proper materials and applying the characteristic provisions covered by this invention, magnetic fluxes of high densities, for instance, 0.1 Weber per square meter or more, can be produced by the permanent magnets incorporated in the chambers for acting on the electric arcs. It is evident that magnetic fluxes of such densities can act effectively and promptly on electric arcs of any intensity so as to cause their rapid and final extinction.

Although I have shown my novel are extinguishing chamber as adapted to be used with conventional circuit interrupters working in an atmosphere constituted by air at normal pressure, it will be clear that are extinguishing chambers of the forms described above, or of any other type, easily designed and constructed according to this invention, can be conveniently arranged in combination with an appropriate container for the purpose of maintaining the electrical and magnetic components constituting the chamberv immersed, for example, in a gaseous insulating medium which can also be capable of assisting in the extinction of the electric arc. In other words, it will be possible to immerse the permanent magnet couple of each of the sections, or the various permanent magnet couples of the sections, constituting the extinguishing chamber within an atmosphere of, for example, sulphur hexafluoride, selenium hexafiuoride, or a mixture of such gases with air, or within an atmosphere of trifiuorimetil-pentafiuoride of sulphur, or of similar gases, or of hydrogen, either at atmospheric pressure or at any convenient higher or lower pressure.

Such are extinguishing chamber constructed according to this invention can also be immersed Within a liquid insulating medium, such as pure water, transformer oil, liquid sulphur hexafiuoride, or similar substances.

The electrical and magnetic components constituting an arc extinguishing chamber embodying this invention can also be conveniently arranged, together with the other members of the extinguishing chamber needed for its operations, within an appropriate container suitable for obtaining and maintaining inside it any convenient degree of vacuum.

It has also to be understood that the types of permanent magnets to be used as well as theirdimensions and combinations, together with the types of the other materials utilized for the realization of an arc extinguishing chamber embodying thisinvention, can be varied if necessary.

. Having described some preferred embodiments of my invention in accordance with the patent statutes, I desire that it be understood that my invention is not to be limited to the particular embodiments disclosed, inasmuch as it will be obvious, particularly to the persons skilled in the art, that many changes and modifications may be made in the embodiments disclosed without departing from the broad spirit and scope of the invention.

Therefore I desire that my invention be interpreted as broadly as possible, and be limited only by what has been expressly set forth in the following claims.

I claim as my invention:

1. An arc-extinguishing chamber, for A.C. arcs initiated upon separation under load of load-carrying A.C. contacts, comprising, in combination, a pair of sections, each including a plurality of parallel permanent magnet couples, extending along opposite sides of the path of travel for relative movement of the contacts, the sections being arranged in facing mirror image relation to each other so that each section acts efficiently on a respective different polarity half-wave of the A.C. current; the parmanent magnet couples of each section being arranged in adjacent relation along the path of the electric arc, with each couple having planar opposite pole faces in facing spaced parallel relation to define therebetween a very narrow air gap in a permanent magnet circuit with each of said air gaps constituting a portion of the arc path; each couple having its polarity reversed with respect to the adjacent couple; insulating walls supporting the magnets of each couple to align the air gap thereof to extend at right angles to said path of travel; and respective paramagnetic yokes connecting the magnets of each couple to each other and constituting a magnetic flux return circuit for the magnets of the respective couple; whereby strong transverse magnetic fields are generated along the arc path and have directions perpendicular to the portion of the arc path defined by the respective air gap across which each magnetic field is effective, so that the arc is forced to follow a serpentine path, of increasing length, through successive air gaps to quickly displace the are away from said path of travel.

2. An arc extinguishing chamber, as claimed in claim 1, wherein said planar pole faces comprise polar shoes formed of a material having good magnetic permeability and have their outer surfacescoated with refractory ceramic insulating material capable of resisting the action of the arc.

3. An arc extinguishing chamber, as claimed in claim 1, in which each section includes a further couple, including permanent magnets, positioned at the zone of immediate separation of the contacts; one of said contacts being movable and the other of said contacts being stationary; and a pair of electrically conductive members each electrically connected to said stationary contact and extending in opposite directions outwardly from said path of travel; said electrically conductive members being positioned, relative to said further couples of permanent magnets, such that the magnetic field of a further couple of permanent magnets acts immediately on the arc root impinging on said stationary contact to force said are root to displace itself along a respective one of said electrically conductive members acting as a guiding horn for the arc root.

4. An arc extinguishing chamber, as claimed in claim 1, in which said yokes comprise flat plates of paramagnetic material projecting outwardly beyond the associated permanent magnets; and prismatic blocks of material having good magnetic permeability and high electrical resistivity interconnecting the plates of each pair externally of said are extinguishing chamber.

5, An arc extinguishing chamber, as claimed in claim 1, wherein said yokes comprise pairs of plates of paramagnetic material each extending outwardly of the respective permanent magnets in substantially parallel relation; and permanent magnets disposed between and interconnecting the projecting portions of said plates; those surfaces of the plates exposed to the arc having a protective coating of refractory ceramic insulating material.

References Cited UNITED STATES PATENTS 2,337,949 12/1943 Walle 200-147 2,645,693 7/1953 Cole et al 20()l44 2,757,261 7/1956 Lingal et al. 200-148 FOREIGN PATENTS 597,353 8/1959 Italy. 1,015,893 9/1957 Germany. 1,146,159 3/1963 Germany.

119,212 7/ 1958 Russia.

110,017 3/1944 Sweden.

ROBERT S. MACON, Primary Examiner. 

